The invention relates to a method for subdividing wafers into chips, in which the wafer is firstly weakened along the separation lines and then broken.
Methods of this type are generally known. The wafer is usually scribed prior to breaking. This method is particularly advantageous since there is no loss of material associated with the separating operation. However, the loss of material is avoided only when a material-dependent ratio of wafer thickness to edge length of the chip is not undershot. This ratio is about 2-2.5:1 in the case of the compound semiconductors GaAs and InP. If this limit is undershot, rear side breakouts, in particular, occur, which reduces the yield. If the chips are to be miniaturized, the thickness of the chips must therefore be reduced as well. However, commercially available wafers have predetermined thicknesses, so that miniaturization of the length dimensions of the chips is possible only to a limited extent.
One object of the invention is to provide a separating method by which thick wafers can be singulated into chips having small linear dimensions.
This and other objects are attained in accordance with one aspect to the invention directed to a method for subdividing a wafer into chips, in which the wafer is firstly weakened along separation lines and then broken along the separation lines. A grid dimension of the separation lines is less than twice the thickness D of the wafer. The wafer is provided with recesses the separation lines in such a way that the ratio of grid dimension to the residual thickness of the wafer in the region of the recesses is greater than or equal to 2:1, and wherein the wafer is subsequently broken.
Stated another way, this object is achieved by virtue of the fact tat a grid dimension of the separation lines is less than twice the thickness of the wafer, and that the wafer is provided with recesses along the separation lines and is then broken.
By sawing into the wafer, the thickness of the wafer is brought locally to the permissible dimension. The wafer can then be conventionally scribed further and broken without the risk of breakouts. The method proposed thus enables thick wafers to be subdivided into chips having small length dimensions.